The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.
Lariciresinol, cyclolariciresinol (also called isolariciresinol) and secoisolariciresinol are all plant lignans known to possess valuable biological properties e.g. in cancer therapy. These lignans are also precursors for the mammalian lignans enterolactone and enterodiol.
Hydroxymatairesinol is also known as a biologically active plant lignan. Hydroxymatairesinol appears as two diastereomers, namely (−) hydroxymatairesinol (also denoted HMR 2 isomer) and (−) allo-hydroxymatairesinol (also denoted HMR 1 isomer).
Considerable amounts of lignans are found in coniferous trees. The type of lignans differs in different species and the amounts of lignans vary in different parts of the trees. The typical lignans in heart wood of spruce (Picea abies) are hydroxymatairesinol (HMR), a-conidendrin, conidendric acid, matairesinol, isolariciresinol, secoisolariciresinol, liovil, picearesinol, lariciresinol and pinoresinol (R. Ekman, “Distribution of lignans in Norway spruce”, Acta Acad. Abo, Ser. B, 39:3, 1–6 (1979). The far most abundant single component of lignans in spruce is hydroxymatairesinol (HMR) (about 60 percent of total lignans) which occurs mainly in unconjugated free form. The lignan concentration in thick roots is 2–3 percent. Abundance of lignans occurs in the heart wood of branches (5–10 percent) and twists and especially in the knots, where the amount of lignans may be higher than 10 percent (R. Ekman, “Analysis of lignans in Norway spruce by combined gas chromatography—mass spectrometry”, Holzforschung 30, 79–85 (1976); R Ekman 1979; Willfor, S., Hemming, J., Reunanen, M., Eckerman, C. and Holmbom, B. (2001): “Hydrophilic and lipophilic extractives in Norway spruce knots.” Proc. 11th Inter. Symp. Wood Pulping Chem., ATIP, Nice.). These concentrations are about hundred-fold compared to ground flax powder known as a lignan-rich material.
It has been suggested to isolate hydroxymatairesinol from compression-wood fiber. These fibers originate from compression wood of stems and knots (oversized chip fraction) and they are known to weaken the quality of paper (R. Ekman, 1976; S. Willför et al. 2001).
It has recently been found that high amounts of hydroxymatairesinol can be produced by extracting finely divided wood material, preferably spruce knotwood, with a polar solvent or solvent mixture and precipitating hydroxymatairesinol from the extract as a complex. Suitable solvents to be used in the extraction step are, for example, pure ethanol or a mixture of ethanol and ethyl acetate. After the extraction step at least part of the solvent is preferably withdrawn before the addition of a complexing agent, which preferable is a carboxylate, such as acetate, of an alkali metal, such as potassium, an earth alkali metal, or ammonium. Such carboxylates form crystallisable adducts with hydroxymatairesinol. An especially preferable complexing agent is potassium acetate, which gives an easily crystallisable potassium acetate adduct of hydroxymatairesinol. This adduct is also rich in the (−) hydroxymatairesinol diastereomer.